Such a compensation device is already known in the art, e.g. from the article "Electrical predistortion to compensate for combined effect of laser chirp and fibre dispersion" by H. Gysel and M. Ramachandran and published in Electronic Letters of 28th Feb. 1991, Vol. 27, No. 5, pp. 421-423. Therein, the optical signal is transmitted from a sending station to a receiving station, and the tunable compensation means, more specifically a varactor diode, is tuned to compensate optimally for a predetermined distance between the sending and the receiving station. It is clear that whenever the transmission distance between these stations changes this distance has to be measured again and the tuning of the varactor diode by means of its bias voltage has to be adjusted to achieve optimum compensation.